Air filter devices for hydrocarbon adsorption in particular with a filter element having activated carbon are arranged in particular in the region of a tank vent in modern motor vehicles in order to prevent an uncontrolled escape of hydrocarbons into the environment. The activated carbon arranged in the filter device in turns absorbs the gaseous hydrocarbons escaping from the tank and delivers them again during operation to an internal combustion engine since it is then that the filter device is flushed in the opposite direction with fresh air. In order to be able to maintain the effectiveness of the activated carbon present in the filter device at a consistently high level for an extended period of time as well, it is necessary to protect it, particularly during the flushing operation, from a moist supply of fresh air. For this reason, long hoses, for example, are used in known filter devices, said hoses additionally forming a siphon with which it is attempted to reduce the moisture content of the air taken up during the flushing operation of the filter device. Disadvantageous with such hose solutions, however, is that their design is time-intensive and costly, while they furthermore require a considerable amount of space.